Recently, various types of image track display apparatus have been developed. These image track display apparatus are useful for clearly illustrating a track of a specified image moving on a screen of a display device. According to the image track display apparatus, a viewer can see moving tracks of various displayed objects, such as baseballs, golf balls, etc.
Some examples of conventional image track display apparatus will be described in brief below.
The Japanese Patent Application; Tokko-Sho P51-12369 discloses a method for displaying a track of a moving image on a screen by multiplexly synthesizing the corresponding storage moving image information by the method of simultaneous reproduction after erasing the static image information, by extracting only the moving image information and storing the corresponding extraction result in the portion of period of a few frames or a few fields, and by subtracting one frame or one field delay video image signal and a non-delay video image signal.
The Japanese Patent Application; Tokko-Sho P62-48432 discloses an image track display apparatus in a video image enabling to display brightly only the track of the desired moving image by automatically moving the position of the window accompanied by the movement of the moving image.
Japanese Patent Application: Tokko-Sho P62-48433 discloses the image track display apparatus in a television screen so that the simplification of a circuit store's image signals of the moving image detected so as to be designed for being successively superposed aiming at the fact that its image signal has the different signal level from the image signal in the background, being normally that the image of a moving image is like a white ball of baseball or golf, enabling to rightly display only the track of the desired moving image by moving automatically also the position of a window accompanied by the movement of a moving image.
The Japanese Patent Application; Tokko-Sho P62-46107 discloses a processing apparatus of image signal enabling to successively projecting a moving image on a television screen along with its track by sampling a digital image signal, storing a signal of difference between its sampling signal and a delay signal of sampling signal in the first and second storage means, installing the switch circuit to alternately select the signal read out, and designing to successively obtain a signal exceeding the specified level by the switch circuit.
Those conventional image track display apparatus, however, require very complicated constructions for extracting and displaying an image track. Furthermore, those conventional image track display apparatus have problems of reliability and cost of the apparatus, due to the complicated construction.